/Engine/Source/Runtime/InteractiveToolsFramework/Public/BaseGizmos/GizmoMath.h
Find the intersection of the ray defined by RayOrigin and RayDirection with the plane defined by PlaneOrigin and PlaneNormal. Returns intersection success/failure in bIntersectsOut and the intersection point in PlaneIntersectionPointOut
namespace GizmoMath { void GizmoMath::RayPlaneIntersectionPoint ( const FVector & PlaneOrigin, const FVector & PlaneNormal, const FVector & RayOrigin, const FVector & RayDirection, bool & bIntersectsOut, FVector & PlaneIntersectionPointOut ) }